Don't depend on String8 cast to C string [audio]

Bug: 295394788
Test: m checkbuild
Change-Id: I73acbfad6da4f18566f6b11889e83679deeaa2b8
diff --git a/audio/core/all-versions/default/PrimaryDevice.cpp b/audio/core/all-versions/default/PrimaryDevice.cpp
index cf162f1..13efbbc 100644
--- a/audio/core/all-versions/default/PrimaryDevice.cpp
+++ b/audio/core/all-versions/default/PrimaryDevice.cpp
@@ -283,7 +283,7 @@
         _hidl_cb(retval, TtyMode::OFF);
         return Void();
     }
-    TtyMode mode = convertTtyModeToHIDL(halMode);
+    TtyMode mode = convertTtyModeToHIDL(halMode.c_str());
     if (mode == TtyMode(-1)) {
         ALOGE("HAL returned invalid TTY value: %s", halMode.c_str());
         _hidl_cb(Result::INVALID_STATE, TtyMode::OFF);